European patent EP 1 068 394 B1 discloses a process for impregnating decorative papers used for the production of highly abrasion-resistant laminate floor materials. In this process the decorative paper is first moistened with an amino resin and impregnated thereby, the amount of the resin being regulated by means of metering rolls, and a layer of an amino resin in a special dispersion then additionally being sprayed onto the top of the moistened wet decorative paper.
The product of the known process, a decorative paper having a uniform coating which comprises an amino resin with particulate silicon carbide, corundum or alumina and comprises no cellulose derivatives, can be pressed onto an HDF substrate board on a short-cycle press at 180° C. while maintaining a press time of 20 seconds. In an abrasion test corresponding to the standard DIN EN 13329, this board had an abrasion value of IP 12 000.
The abrasion test corresponding to the standard DIN EN 13329 envisages that two friction wheels equipped with emery paper strips are used in a special test apparatus in the holder of which the test specimens are clamped, where they are brought into contact with the friction wheels. After 100 revolutions in each case, the test specimens are checked for abrasion, and the emery paper is replaced by fresh emery paper after 200 revolutions in each case. The test is continued until the so-called initial abrasion point (IP) is reached. This is understood as meaning the point at which a decorative print present in the test specimen is worn through for the first time in a clearly detectable manner under the conditions defined in detail in the standard. The number of revolutions required for reaching this point is recorded and is a measure of the abrasion resistance. The IP resistance of a laminate floor to abrasion is then stated in abrasion classes according to DIN EN 13329 as shown in Table 1.
TABLE 1AbrasionRequirement (IP value)classNumber of revolutionsApplicationAC1at least 900BedroomAC2at least 1500Living roomAC3at least 2000LobbySmall officeAC4at least 4000HotelAC5at least 6000Department store
A similar classification is also found in the standard DIN EN 438 “High-pressure decorative laminates (HPL)—sheets based on curable resins (laminates)—Part 2: Determination of the properties”.
In European patent EP 1 068 394 B1, no print layer on the decorative paper is mentioned for the product of the process described. However, it is customary in practice to use in addition to unprinted tinted, papers, printed papers whose printed image is then covered by the particle-containing abrasion-resistant layer. In this process, it is possible for the optical impression of the decorative sheet to suffer in a disadvantageous manner. Any special optical effects strived for are thus reduced, lost, or not achievable at all.
DE 103 34 008 A1 describes a process for coating substrate materials of different gloss zones and a substrate material produced by said process. According to this process, the substrate material is subjected in succession to a plurality of printing processes with matte and glossy coatings being either colorless or colored when applied. In particular, a decorative sheet having different gloss zones is produced.
The furniture and laminated flooring industries are continually striving to improve or enhance the performance of its products, such as abrasion resistance and optical effects, without significantly impacting either cost or ease of manufacturing. In this regard there is a need in the industry to continually develop novel materials and new manufacturing processes for the production of abrasion resistant sheets, such as overlays, to be used in laminate flooring or furniture surfaces.